This invention relates to integrated circuit diagnosis, characterization, and modification using focused ion beam (“FIB”) systems.
FIB systems can be used to micro-mill, perform local deposition, and measure local electrical potential on an integrated circuit (“IC”). Operations such as these, i.e., operations on an IC that are performed using a focused ion beam, will be referred to in this specification as FIB operations. FIB systems are powerful tools because they can be used to perform many IC editing operations, such as circuit repair and modification, as well as IC characterizing operations, such as testing and debugging.
FIB operations have traditionally been performed on the front-side of an IC. The implementation of face-down or flip-chip packaging has created severe limitations for the use of FIB systems because such packaging leaves only the backside, also referred to as the substrate side, of the IC exposed and visible.
Integrating infrared (“IR”) imaging devices into a FIB system allows one to perform FIB operations on the backside of an IC. IR light can penetrate a silicon substrate, allowing an operator to find structures of interest situated beneath the substrate. In this context, a structure of an IC can be part of a circuit element of the IC. When an IR imaging device, such as an IR microscope, is integrated into a FIB system, the FIB system can use the IR device to navigate to a structure of interest and then perform FIB operations.
Using blind navigation also allows one to perform FIB operations on the backside of an IC. With blind navigation, one or more fiducial marks on an IC are exposed and used as reference points to navigate to a structure of interest.